Causes:

Erythema multiforme

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Coagulation cascade and assessment

Platelet disorders

Normal platelet turnover

Produced by fragmentation of cytoplasm of megakaryocytes in the bone marrow.
Production is regulated by negative feed back involving thrombopoietin.
Normally, platelets are removed by macrophages of the reticuloendothelial system.

Bleeding disorders due to platelet problems

Presents with purpura and mucous membrane bleeding.
Purpura can occur when plt count is < 50k.
Presentation is similar to bleeding in vascular disorders.

Causes of thrombocytopaenia

Impaired production, increased destruction, splenic sequestration.

Causes of impaired platelet function

Disorders of platelet function are suspected in patients who show skin and mucosal haemorrhage despite a normal platelet count and normal levels of VWF.

Platelet count is often normal, bleeding time is prolonged.

Glanzmanns thrombasthenia

#autosomal-Recessive defects in GPIIb or IIIa -> defective platelet aggregation.
Presents in neonatal period.

Bernard soulier syndrome

#autosomal-Recessive Defective adhesion and aggregation. Larger than normal platelets.
Presents at birth; mucosal and post traumatic bleeding.

Storage pool diseases

Lack of storage pool of platelet dense granules.
? age of presentation

3. Frontalis muscle - mostly lifts the eye brows.

Causes of ptosis

• Congenital ptosis: Absence of LPS muscle; usually unilateral and non progressive.
• Marcus Gunn jaw winking - aberrant innevervation of the LPS bi the trigeminal nerve. Eye open when chewing.
• Aponeurotic - Most common cause of acquired ptosis in adults. Dehiscense of the levator aponeurosis. Can occur with old age related involutional change or use of contact lenses.
• Mechanical - infection, inflammation, eye lid tumour etc.
• Neurologic:
  • Local OR systemic problems affecting the pathway from the nucleus of CN3 in the midbrain all the way upto the LPS muscle.
    • CN3 Palsy
    • Horner syndrome
    • NMJ disorders -
      • ptosis is uncommon in Lambert eaton syndrome,
      • Myasthenia gravis
      • botulinum toxin (if infectious botulism, other systmic signs will be present)
• Myogenic -
  • mitochondrial myopathy
  • Oculopharyngeal muscular dystrophy (OPMD) is a rare, autosomal dominant myopathy

Anatomy of the CNIII nucleus

Within the CNIII nucleus, each muscle innervated by the nerve as a subnucleus.

1. Subnucleus of LPS is not paired -> lesions cause bilateral ptosis.
2. Most muscles are innervated by the ipsilateral nulcei.
3. Except for Superior rectus - innervated by contralateral nucleus.
   

Symptoms of unilateral CNIII nucleus lesion

[!INFO] Unilateral lesion peculiarities
Note: Bilateral eye elevation deficit and ptosis

Location of the sympathetic fibers

Isolated oculomotor nerve palsy with pupillary involvement in adults is usually related to compression of the third nerve either by an intracranial aneurysm, typically originating at the junction of the posterior communicating and the internal carotid arteries, or by a pituitary tumor (such as in pituitary apoplexy). Both disorders are life-threatening conditions.

Pupil sparing CNIII palsy

I.e All muscles affected but pupils spared.
Selective ischemia of the central part of the nerve, not affecting the peripheral sympathetic fibers can occur in occlusion of the vaso nervorum. (eg. Diabetes mellitus)

Synegistic with penicillins used in endocarditis against Enterococcus and streptococcus viridans.

Paralysis usually resolves in about 4 days with complete EMG resolution taking about 6 weeks.
Resolution of paralysis progresses upwards.
No chronic neurological deficits were reported.